The car in question is a 98 S500 sdn w/ 65k. I bought the car about a month ago and when I checked the oil it seemed to be overfilled (i.e. the oil level on the dip stick was about 3/8 to 1/2 inch above the max line). The next morning I set out to drain some oil to get to the correct amount. So I took off the oil fill cap to siphon some oil out with an old turkey baster. However, before I began to siphon the oil I decided to check the oil again and got a reading that was fine (right at the max line). I figured I would drive around for 20 minutes to warm the engine and see if the reading was still high before I started draining the oil. That seemed fine, until I was driving for about 15 minutes and there was smoke coming from under the hood. The smacked ass that I am, I forgot to put the oil cap back on, so oil spilled all over the engine bay! What a fool!

Anyway, since then (three weeks) I changed the oil and the car has been running fine. Yesterday, I decided to change the plugs and when I took off the black cover that houses the coil and sparkplug, I noticed that there was some oil in there. I cleaned that up and began to change the plugs. When I took off the coil to get to the plug, there was a considerable amount of oil in the sparkplug well (put it this way, there was enough oil to cover the entire spark plug socket). I unscrewed the plug and cleaned out the well. This oil was in each of the 4 plug wells on the same side as the oil fill cap (passenger side).

My Questions:
1) Could the oil have gotten in there from me leaving the cap off? My guess is yes.

2) When I took the plugs out, there was oil all over them, including the tip where the spark is made. For oil to be covering the tip, that would mean that there was a big problem, a cylinder was leaking oil (or 4 cylinders since all four plugs had oil), correct? I am just uncertain if the tip of the plug was just oil filled from when I pulled it out, or if there is a leak. My guess, is that it was covered in oil from when I pulled it out b/c if there was oil where the plug makes the spark, the car would have been running like **** and smoke would have been everywhere, correct?

Everyone's help would be greatly appreciated. Hopefully, this is just a non-issue and will be resolved inexpensively.

Feel free to laugh or mock me for leaving the cap off, I deserve it, but only if you give me some insight to my questions.

Thanks

The only way to avoid mistakes is to do nothing. But that's a mistake in itself!

Leaving the cap off will account for your oil contamination. The oil on the plugs will probably have come from the oil in the plug wells. Spark plugs run hot and burn off any oil that gets on them. What you see from oil burning is black tarry residue. If you had liquid oil it was from your oil contamination.

Relax, enjoy your car.

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Cheers, Neil

Thanks neileg!

That's what I suspected, but was unsure.

When I started the car after replacing the plugs, I got a whole lot of smoke (think smoke bomb) out of the exhaust. I suppose from when I took out the spark plugs the oil drained out of the well and into the are where the plugs ignite. Is it safe to assume that the oil was just burning out of that chamber and everything is fine? Also, will these new plugs be fouled b/c of this?

Thanks again

Check your oil with the engine hot, and wait about five minutes for the oil to drain into the pan. Checking it cold will give an inaccurate reading.

You're lucky with that filler cap. When I was in high school a friend of mine had a Chevy Nova. We filled his crankcase after an oil change in shop class. He forgot to install the filler cap. When backing out, the filler cap fell into the fan, and the fan shot the cap out through the rad like a missle. Since that day, I am a fanatic about checking the filler cap.

Oil in the cylinder will cause the smoke. The new plugs may be fouled, and the only way to tell may be to pull them. How is the car running now? Any more smoke? Did you get a CE light?

Before pulling the new plugs out, drive it for a few weeks at leasts and see what happens.

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John Shellenberg
1998 C230 "Black Betty" 240K

http://img31.exs.cx/img31/4050/tophat6.gif

Tell me about it, I drove on the highway and through the city with the cap sitting on top of the crankcase. It never moved! I can't believe it didn't fall off. Good thing the same thing didn't happen as with you buddy's car.

No CE light but a lot of smoke when I first started it. Unfortunately, I only ran the car for about 5 minutes b/c I had to go to work. I will check it out more thoroughly when I get home tonight. At just over $9 per plug I hope they are not fouled out. Apparently, starting in 98 they changed the plugs for the 500. From 92-97 they were the same. I suspect they changed to 100k plugs in 98 - I do know that they are platinum. If there is some buildup on the plugs when I go home tonight, is there a way to clean off the tip of the plug? I just hate throwing money away!

Thanks

If your plugs are fouled the engine will run rough. If the engine is running smoothly, leave your plugs alone and go and play some pool or have a round of golf.

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Cheers, Neil